class Solution {
public:
    int combinationSum4(vector<int>& nums, int target) {
        vector<unsigned> dp(target + 1, 0);
        dp[0] = 1;
        for(int i = 1; i <= target; ++i)
        {
            for(int x : nums)
                if(i >= x) dp[i] += dp[i - x];
        }
        return dp[target];
    }
};
